The present invention relates to surgical drapes, and more particularly to surgical drapes formed from a polymeric film having a low glare finish and a predetermined coloration for selectively reducing the luminous intensity of light reflected from the surface thereof.
The complete visual system requires light, the eye, and a conscious observer. The visual system is especially well adapted for rapid and precise visual extraction of spatial information from a more or less remote external world, doing so by analysis of the continuously changing patterns of radiant flux impinging upon the surfaces of the eyes. Much of this light is reflected from objects which must be discriminated, recognized, attended to, and/or avoided in the environment, all the while transcending enormous variations in intensity, quality and geometry of illumination as well as the vantage point of the observer.
Light (i.e., visible light) represents only one portion of the electromagnetic spectrum, namely the portion laying between radio waves and x-rays, more particularly those electromagnetic waves possessing a wavelength between about 380-770 nanometers (nm) . The lighting or illumination of a surface is the luminous flux which it receives per unit area (i.e., luminous flux is a measure of the power of visible light) . Common units for luminous flux (i.e., illuminance) include the foot-candle (i.e., 1 lumen per square foot, or the foot lambert), and the lux (i.e., 1 lumen per square meter). Minimum recommended task based lighting levels are provided by General Electric Company as follows: casual, 30 footcandles (fc); rough, 50 fc; medium, 100 fc; fine, 500 fc; and, extra-fine, 1,000 fc.
Color is a characteristic of light that produces specific degrees of hue, saturation and brightness, with most color models of perceived color containing these three components. For instance, in the International Commission on Illumination (CIE) xe2x80x9cL*a*b modelxe2x80x9d, color is modeled as a sphere, with lightness comprising the linear transformation from white to black, and hues modeled as opposing pairs, with saturation being the distance from the lightness axis.
Chromaticity (i.e., apparent color temperature or correlated color temperature) is the measure of a light source""s xe2x80x9cwarmthxe2x80x9d or xe2x80x9ccoolness,xe2x80x9d expressed in the Kelvin (xc2x0 K.) temperature scale. It describes the appearance an object would have if it were heated to incandescence (i.e., the point of emitting light) then to higher temperatures where the appearance changes from ruddy red through a range of warm colors to white, then finally to blue-white. Selected sources of illumination and their color temperatures include: candle flame, 1850xc2x0 K.; sunlight (sunrise/set), 2000xc2x0 K.; sunlight (mean noon), 5400xc2x0 K.; 40 watt incandescent tungsten lamp, 2650xc2x0 K.; 100 watt incandescent tungsten lamp, 2865xc2x0 K.; 500 watt incandescent tungsten lamp, 2960xc2x0 K.; photoflood/reflector flood, 3400xc2x0 K.; white flame carbon arc lamp, 5000xc2x0 K.; and, xenon arc lamp, 6420xc2x0 K.
The human eye includes various muscles which, like any part of the human body, will tire and strain when kept in a fixed configuration for sufficiently long periods. Immediate symptoms of eye fatigue and eye strain include headaches and difficulty focusing one""s vision. In the long term, prolonged or severe eye fatigue and strain may decrease the strength of eye muscles and require corrective lenses, or an increased prescription for those already requiring corrective lenses.
When an object is too close to a viewer, the viewer is forced to bring his or her eyes inward (i.e., towards their nose). The motion of the eyes turning inward is called convergence. Convergence requires intensive exertion of the eye muscles, in particular the ocular muscles. When the eyes are not properly relaxed through either visual exercise or rest, the viewer may experience eye fatigue and/or eye strain. Repeated and/or prolonged convergence can permanently decrease the strength of the eye muscles.
In addition, a viewer""s eyes must focus in order to properly perceive an object. Focusing causes strain to the viewer""s eyes. In order to focus on close objects, the eye""s lens thickens. That is, the closer an object to the viewer, the thicker the eye""s lens must shape themselves. Thickening the eye""s lens is particularly exhausting on the eye muscles, serving to exacerbate the fatigue and strain brought on by the convergence that also accompanies viewing close objects.
One result of eye fatigue and eye strain is a diminished synchronization between a viewer""s pair of eyes. That is, the viewer""s left and right eyes are not working synchronously to provide the visual information required to visually perceive one""s surroundings. Accordingly, common orthoptic tests involve monitoring the eye""s ability to synchronize, while common orthoptic treatments involve the viewer performing eye exercises that promote synchronization, either through stretching and strengthening the eye muscles, or via forced relaxation.
Some of the most common causes of eye fatigue and/or strain include viewing close objects, viewing objects displayed on a light emitting medium, and simply viewing images for excessive time periods. Reading or doing close work in extreme light conditions, whether bright or dim, for extended periods forces the eyes to focus under less than optimal conditions, and thereby contributes to eye strain, symptoms of which may include; headaches; blurred vision; pain or soreness of the eyeball; red/watery eyes; dry eyes that feel scratchy; tired, aching heaviness of the eyelids or forehead; back and neck aches; and, muscle spasms.
Glare is a similar phenomenon which contributes to eye strain, in addition to mitigating visual acuity. The contrast between the image being viewed and its background is reduced by reflected light, making it harder for the brain to interpret the image. Facial and eye muscles tighten as the eye unconsciously strains to send a clear signal to the brain.
A particularly harsh visual system setting, or environment, for the eyes is a hospital operating room. In addition to the requirements of up-close high precision work, which in and of itself is stressful, high intensity surgical lighting systems are present to aid the surgeon and his or her team. Such lighting systems are known to deliver up to, and in excess of 140,000 lux (i.e., lumens per square meter, or about 13,000 fc) at about 4500xc2x0 K. chromaticity. Working for long periods of time, anywhere from one to eight plus hours per procedure, under such light conditions is more often than not the cause of eye fatigue and/or strain. Alleviation or mitigation of the source of such stress to the visual system would be most welcome. Such improved working conditions, as minimal as they might seem, may be of paramount importance to those who rely upon the skill and execution of the surgeon.
A surgical drape manufactured or fabricated from a polymeric film having a low glare finish and a predetermined coloration for reducing the luminous intensity of light reflected from the surface thereof is provided. Such surgical drape thereby minimizes reflectivity therefrom, and thus eye strain and fatigue. The subject invention includes the use of colorants, dyes, pigments, etc. to form translucent polymeric surgical drapes that absorb a selected range of wavelengths from surface reflected light. Furthermore, the subject invention includes such energy absorbing drape having a textured surface to effectuate a reduced reflectivity. More particularly, the use of coloring agents in combination with a textured surface yield a surgical drape possessing reduced luminance and glare, thereby mitigating eye strain and fatigue. The preferred range of reflected light, in order of preference, is 625-700 nm, 520-560 nm, 450-520 nm, 400-450 nm, 600-625 nm, and 560-600 nm. More specific features and advantages will become apparent with reference to the DETAILED DESCRIPTION OF THE INVENTION, appended claims, and the accompanying drawing figures.